At he same time, muffler styles and evaluation of acoustic performance and analysis methods of acousticcharacteristic are introduced detail by detail.
同时，对消声器的分类，消声性能评价以及消声特性分析方法进行了详细的说明。
2
Based on analysis of spectral characteristic of helicopter acoustic signal, a method of extracting harmonic frequencies from the helicopter acoustic signal via ESPRIT is proposed.
A recognition method based on gray correlation analysis algorithm is proposed through extracting LPC, characteristic from tank, helicopter and car acoustic.